The invention relates to a roof for the melting area or working area, or fining end or the like, of a glass melting furnace (tank) made of refractory material.
In a glass melting furnace it is common practice to connect to the actual melting tank output a working tank having a feeder which contains molten glass in mass flow. The roof of the melting and working tank is usually formed by an arch.
The working tank serves mainly for feeding the glass coming from the throat into the feeder or feeders. The purpose of the latter is to bring the glass, by heating or cooling it, to the working temperature, which differs according to the product. This has not, however, been possible, especially to the degree desired combined with uniformity of temperature throughout the mass, if the feeders are very short, for example, or the glass comes from the throat at too high a temperature, for example, or if there are frequent changes of load.
For these reasons it is desirable to precondition the glass in the working tank, so that the glass, when it enters the feeder or feeders, will be brought to a temperature that is as close as possible to the desired gob temperature, while preserving homogeneity.
Working tanks are known in which such preconditioning is performed. These are working tanks which are disposed in the form of a feeder channel that runs usually across the long axis of the furnace. To heat and cool the glass and to cover the channel, systems similar to those commonly used on gob feeders are used.
Usually, however, working tanks are constructed in any desired ground plan, the size of which often amounts to about 10 to 20% of the melting tank area and whose shape is determined by the arrangement of the machines, i.e., it is irregular.
Such working tanks usually have an undivided combustion chamber, a distance between the glass bath surface and the arch or dome of more than 50 cm, and can usually have only an overall temperature control. The installation of stirrers or thermocouples is very difficult on account of the great distance between the glass bath and the arch.
The construction of the furnace superstructure is very complex, since the arch can be made only from relatively small-size bricks.
An efficient control of the parameters of the state of the molten glass from the roof has been neither customary nor feasible heretofore. This also is true of the actual melting tank. It was therefore possible that, in spite of all experience on the part of the operators and all manipulation of the means for temperature control, the state of the glass melt, which can be determined only in the area of the gob feeder, might not always be optimal.
The invention is addressed to the problem of designing a substantially improved form of a working tank and feeder on a glass melting furnace having a tank covered by a radiation roof made of highly refractory glass furnace brick material and containing molten glass in mass flow, and having at least one gob feeder disposed on the tank, in order thereby to exercise adjustment and control over the necessary and anticipated parameters of the state of the molten glass in a continuous manner along the path over which it flows from the melting tank through the fining end to the gob feeders. For this purpose the configuration of the working tank and especially of the radiation roof is to be uncomplicated, permit access to the molten glass without difficulty at different points for inspection and testing, and permit the use of means for controlling the temperature. It is also to be possible to place temperature and/or viscosity measuring apparatus at an especially appropriate point on the fining end, and to bring into contact with the glass melt, at a suitable point, heating or cooling elements as well as means for controlling convection, such as stirrers or damming elements.